The present invention pertains to interconnection of automatic test systems to a telecommunication switching system and more particularly to an arrangement for facilitating loop analysis testing of subscribers of a digital switching system.
Historically, loop analysis testing of subscriber lines connected to step-by-step or electromechanical switching systems was accomplished by external or internal loop analysis test systems (LATS) by obtaining a metallic path through the switching system to the particular subscriber's line. In situations where such loop analysis testing was incidental to a cut-over of a subscriber's line from a step-by-step to an electromechanical switching system, two paths would be established to the subscriber's line appearance in the switching office. The first path would be through the electromechanical switching system and the second path would be through the step-by-step switching system. The LATS system could then utilize both of the systems to have one system ring the subscriber's line and the other to detect that ringing was applied to the proper line.
In this manner, the data base of the electromechanical switching system could be verified for integrity. In addition, once the cut-over of the subscriber's line from the step-by-step to the electromechanical switching system was achieved, the LATS system could then provide in and out testing functions for the subscriber's line appearance on the electromechanical system.
With the advent of digital PCM switching systems in the telecommunications industry, the solid state and time division switching techniques of these systems prohibit the establishment of a metallic path through the switching network for testing of a subscriber's line. These metallic connections form the basis of the seizure of a subscriber's line for loop analysis testing systems. As a result, present LATS systems are unable to perform the required DC tests to verify the portion of the subscriber's line from the switching system out to the subscriber's handset via the outside plant facilities. In addition, the lack of a metallic path prohibited "in testing," that is, testing the path from the appearance of the subscriber's line inward toward the network of a switching system.
A solution to the problem of providing a metallic test path through a digital switching system to facilitate LATS testing, is to incorporate a controller function in a stand alone arrangement. This stand alone controller would be connected between a LATS system and a digital switching system. One such arrangement is shown by an article published in the GTE Network Systems World-Wide Communications Journal, Fourth Quarter, 1983, Vol. 21-4, entitled GTD-5 EAX LATS Access Controller, by George Verbaas. This system provides a sophisticated computer controlled stand alone system for automatically simulating a human craftsperson's interaction with a digital switching system. This controller might be used to interface a toll board or a local test board to a digital switching system.
However, that arrangement does not make efficient use of the computing power of present day digital switching systems and the availability of certain functional equipment already within the digital switching systems. This stand alone equipment is expensive and requires considerable floor space, which is at a premium in modern day digital switching systems.
In addition, the problem of providing a metallic path for testing in such an environment remains unsolved.
Accordingly, it is the object of the present invention to provide a LATS system interface to a digital switching system utilizing the facilities of the digital switching system in an inexpensive and space efficient manner.